Traffic was brought to a standstill in the busy port of Dover as anti-immigration protesters marched in opposition to migrant crossings.
Lorries were forced to line up along the A20 as protesters with smoke flares blocked the route to the key trade terminals on Saturday afternoon.
There were sporadic clashes with police and several arrests have been made, the PA news agency understands.
A heavy police presence was in place at the Kent port, which has seen violent disorder in the past.
The protests were condemned by Dover MP Natalie Elphicke, who said: “It’s time to stop the small boats crossings but today’s protesters are not welcome in Dover.”
About 50 people, many carrying England flags, marched along the dual carriageway towards the town amid a heavy police presence.
There were chants of “English streets” from the small group of mostly men, many of whom had travelled from outside the area.
One protester, reclining on the tarmac in front of police, remarked: “If you can’t go abroad, lie in the street in Dover.”
At one point, a woman walked into the group of anti-immigration protesters to loudly confront them and was met with shouts.
Kent Police said four people were arrested, two on suspicion of public order offences and two on suspicion of obstructing the highway.
Officers were seen pursuing one man through the town and past a busy fun fair before detaining him in a shop.
Protesters had largely dispersed by around 3.30pm.
Superintendent Andy Gadd said: “Today’s protest has taken place with minimal disruption to the local community. Four people have been arrested and our inquiries into those incidents continues.
“I’d like to thank the local community and those travelling through the area for their patience and understanding as we worked to balance the rights of those taking part in the protest with those living and working in Dover.”
Commenting on the demonstrations, Tory MP Ms Elphicke said: “Time and again we see that the protesters’ day out causes direct damage to someone else’s livelihood, tourism, business and trade. That’s not right or fair.”
She said Kent Police have had a “challenging year”, including border issues in the winter, pandemic policing and the killing of PCSO Julia James.
She added: “They deserved a proper bank holiday break this weekend – not being sworn at by loud-mouthed protesters from London or Essex or wherever.”
Saturday’s protest comes as people continue to make the dangerous journey across the English Channel in small boats.
About 25 people wearing lifejackets and face masks were seen being brought into the port by Border Force earlier on Saturday.
The number of people crossing the 21-mile stretch of water has almost doubled so far in 2021, with more than 3,100 reaching the English coast.
Dover – one of the UK’s most important trade links with continental Europe – has been the target of anti-immigration protests in previous years.
A demonstration last September saw anti-migrant protesters bring traffic at the busy port to a standstill in a similar fashion amid sporadic clashes with riot officers.
The protests in 2020 – carried out amid the shadow of the coronavirus pandemic – saw 10 people arrested.
In 2016, bricks and smoke bombs were thrown amid violent scenes in the port town as officers in riot gear and dog handlers struggled to keep order.
During that incident, flag-waving demonstrators from the National Front and the right-wing South East Alliance marched to protest against the arrival of immigrants.